Mixing machines with ploughshare-like mixing tools have been known for a long time and have proven suitable for a wide variety of mixing problems. These mixing tools plough through the material being mixed located in a drum-shaped or similar mixing container and in so doing produce not only a mixing effect but also lateral conveying, i.e. conveying of the material being mixed in the axial direction of the mixing container. In the past, it was always necessary to treat the material being mixed as gently as possible, so the mixing tools were designed as bodies which were as thin as possible, i.e. the projection of the lateral cheeks on a plane normal to the direction of travel of the mixing tool was kept small so that the material being mixed resists the mixing tool passing through it as little as possible and no accumulation of material forms in front of individual mixing tools, but instead the material being mixed passes by the lateral cheeks of the body of the mixing tool member with as little obstruction as possible. However, it being desirable to treat the material being mixed as gently as possible, it is necessary, in order to achieve a predetermined mixing result with prior art ploughshare-shaped mixing tools, to allow for relatively long mixing times which, in turn, are detrimental to gentle treatment of the material being mixed.
Mixing machines with paddle-like mixing tool members are also known. The mixing tools are placed obliquely to their direction of travel and therefore stress the material being mixed to a greater extent. It has however been found that mixing tools of this type operate with relatively poor efficiency, so that in spite of the greater force on the material being mixed, the mixing time cannot be reduced. In many cases, an accumulation of material also builds up in front of paddle-like mixing tools of this type, and this accumulation certainly contributes to the fact that the mixing times are relatively long.